You can cut the pipe nipples down. Just mount them in a vise, and use a grinder with a cut off wheel, and you can cut them down to the size you need. You will need to clean up the threads with a little bit of hacksaw and diamond file when you are done though. I just re-plumbed an old trailer house for a friend and I had to cut quite a few pieces down just that way to get everything to fit without tearing into the walls.